The document DE 102 48 195 A1 discloses a procedure for monitoring a function of a control unit of an automotive vehicle.
The field of use of the invention is the control of double clutch systems and related, automated clutch systems in automobiles equipped with an incremental path measuring feature for determining the position of the clutch. The invention is a safety function and serves as a component part of a safety system guaranteeing the functional safety of double clutch systems and related, automated clutch systems.
Safety functions are built up so that, as long as no error is indicated by the safety function, there is no error in the procedure carried out and/or monitored by the safety function, and also no error in the system with which the procedure is carried out, because all actions or reactions of the system related to the procedure are taken into account.
Automated clutches, i.e. clutches operated by an actuator, are being increasingly used in modern automotive vehicles. The position of an operating member of the clutch, i.e. of the actuator is generally captured with the help of an incremental counter which supplies information directly only on the just traversed adjustment paths but no information on the absolute position of the operating member. For finding out the absolute position, a referencing is required in which a pre-defined operating position of the clutch is targeted by the actuator and the respective count of the incremental counter is read out.
A fundamental problem of such incremental path measurements is their dependence on the exact determination of the reference position. This problem is aggravated by the fact that errors in the operation of a vehicle have to be basically expected, so that the absolute position of the clutch actuator or operating member of the clutch and, thus also, the clutch torque produced by the actuator are no longer known in the electronic control device. Safety-critical events, for example an unintentional starting of the vehicle, can be the result. Of particularly critical importance for safety is an exact knowledge of the operating position of the clutch at any time in a double clutch transmission in which two clutches are required to be operated in exact coordination with each other.